The present invention relates to water pumps, for example, for motor vehicles.
Water pumps for motor vehicles are known which comprise a pump housing to be fixed to the body of an engine, an antifriction bearing having its outer ring press-fitted in the housing, a pump shaft attached to the inner ring of the antifriction bearing and having an impeller fixed thereto at its one end inside the engine body, a pulley mounted on the pump shaft at the other end thereof outside the engine body, and a mechanical seal provided between the housing and the pump shaft and positioned between the antifriction bearing and the impeller. By driving the pulley with a belt, the impeller is rotated to circulate cooling water.
However, the conventional water pump described has no partition between the antifriction bearing and the mechanical seal, so that the water passing through the mechanical seal exerts a direct influence on the bearing to cause damage to the water pump. Stated more specifically, the mechanical seal portion develops heat through friction because of the construction of the seal, allowing the heat to vaporize water in the vicinity of the seal portion and permitting the water vapor to pass through the seal. The water vapor passing through the mechanical seal immediately condenses to water droplets, which adhere to the end face of the antifriction bearing opposed to the seal. Thus, water passes through the mechanical seal and enters the bearing. Consequently, the bearing becomes damaged owing to corrosion or improper lubrication to render the water pump inoperative. Further since the pulley is fixed to the end of the pump shaft to place a load on the shaft end, a bending force acts on the bearing and adversely affects the life of the bearing.